#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int main()
{
	double a = 1.0;
	int  b = 0;
	double sum = 0;
	for (int i = 1; i <= 100; i++)
	{
		a = 1;
		b++;
		if (0 == b % 2)
		{
			a = -1;
		}
		sum += a / b;
	}
	printf("%lf", sum);
	return 0;
}

